Abstract: A directional power detector mounted between the power amplifier and antenna which supplies audio frequency output signals indicative of forward and reflected power, circuitry for summing and converting the output signals from the power detector means to a DC potential proportional to the magnitude thereof and a transistor connected in shunt at the input of the power amplifier and controlled by the DC potential for controlling the peak envelope power at the antenna.

Abstract: A variable resistance circuit comprising a field effect transistor, a plurality of amplifiers and a feedback circuit for one of the amplifiers with the equivalent resistance value derived from a circuit comprising the field effect transistor electrodes and a reference resistor being controlled by a digital signal or a pulse-width signal supplied to the feedback circuit.

Abstract: In a signal compressor wherein an amplified and smoothed control signal is employed to control a variable gain or variable impedance device, a switch is provided to connect a positive feedback loop across the control signal amplifier, thereby to place the compressor in an oscillator mode for providing an alignment or calibration signal of stable amplitude.

Abstract: An improved circuit is provided for a known amplifier having complementary input transistors in its power output stages for supplying oppositely phased signals in response to an input signal. Output transistors are connected to the input transistors to provide output signals for the amplifier. Normally conducting switching means are connected between one of the output transistors and one of the input transistors. Normally nonconducting switching means are coupled between the one output transistor and the amplifier input. During an overload or overdrive condition, the normally conducting switching means become nonconducting, and this in turn causes the normally nonconducting switching means to become conducting, and thereby limit the output from the amplifier.

Abstract: A gain control circuit utilizing a novel bidirectional transistor connected in shunt with a pair of outputs of a differential amplifier circuit. The novel bidirectional semiconductor device has its conduction level controlled by a variable bias source in its base circuit. By adjusting the bias source, the impedance of the bidirectional device is controlled, and hence the magnitude of the output signal developed across its terminals is controlled in gain.

Abstract: An audio compressor amplifier including an operational amplifier with compressor means connected from the output to the input for compressing signals at the output to a predetermined constant level in a predetermined attack time and including a plurality of diodes connected to reduce the series resistance in the compressor means for decreasing the attack time when the output signal exceeds the predetermined constant level by a predetermined amount, and a gain control feedback resistor connected from the output to the input of the operational amplifier and including a second resistor and a plurality of diodes connected in parallel therewith to reduce the gain of the operational amplifier and provide peak limiting action when a signal at the output exceeds a predetermined value in excess of the predetermined constant level.

Abstract: Signal voltage to be limited is applied across a voltage divider comprising a resistor and a controllable impedance element that includes a pair of transistors. The emitter-collector circuit of the transistors is connected in parallel but in opposite polarity, and the output signal voltage is obtained across the controllable impedance element. For limiter operation, a feedback circuit produces a control current based on a signal voltage and applies the control current to the bases of the transistors to control the impedance thereof. When limiter operation is not desired, elements in the feedback circuit are grounded to reduce the controlled current to leakage value. Even the leakage current is prevented from reaching the bases of the transistors by means of a circuit rendered non-conductive in series with the control current circuit.

Abstract: The compressor part of a compander uses a differential amplifier to receive voice signals. Diode attenuator circuits are connected to the differential amplifier output and attenuate the differential amplifier output signals as a function of a rectified signal derived from the compressor output. The expander part of the compander also uses a differential amplifier to receive voice signals. The differential amplifier is interconnected by a diode attenuator circuit which varies the gain of the differential amplifier as a function of a rectified signal derived from the expander input. The compander thus requires no inductors and uses components which are relatively small and compact.

Abstract: A variable-gain amplifier comprises a transistor with an emitter connected in a degenerative emitter-follower circuit which includes a PIN diode traversed by a current injector in the form of an operational amplifier, the PIN diode forming part of a negative-feedback path extending from the output to the inverting input of the operational amplifier. To achieve a gain characteristic whose logarithm varies linearly with a control voltage, this control voltage is fed to the same inverting input through an amplifier circuit with an exponential characteristic, including another operational amplifier provided with an input transistor. A temperature-compensating circuit, preceding that input transistor, comprises still another operational amplifier having a further transistor inserted in its negative-feedback path. The variable-gain amplifier may be included in one of two conjugate (sum and difference) channels of a monopulse radar.

Abstract: An intermediate frequency amplifier stage includes a tuned circuit which is shunted by a transistor utilized as an emitter follower, the emitter follower being responsive to the amplitude of a detected signal to lower the "Q" of the tuned circuit as the amplitude of the detected signal increases and to increase the "Q" of the tuned circuit as the amplitude of the detected signal decreases, thus effecting the gain of the intermediate frequency amplifier stage inversely respective the amplitude of the detected signal.